Coaxial pipe for the boiler: advantages, disadvantages and installation instructions

Coaxial pipe for the boiler: advantages, disadvantages and installation instructions
Coaxial pipe for the boiler: advantages, disadvantages and installation instructions

Modern gas boilers are reliable equipment that can provide us not only with heat in the house, but also with hot water. But for their proper operation and high performance, it is necessary to install a special chimney. It must perform two main functions at once: supplying oxygen to the burner and removing combustion products outside the room. For this, a coaxial pipe is used. Let's talk about what it is and what its features are.

coaxial pipe

General information

We will not talk now about any design features of heat generators. It is enough to understand that a chimney is necessary for their effective operation. Here the situation is the same as with the most ordinary wood-burning stove. Of course, the coaxial pipe for the boiler has a completely different design, and its installation is carried out with its own nuances, which will be discussed below. So, the key feature of such a chimney is that it works on the principle of "pipe in pipe". It turns out that we have two pipes: one smaller and the second largerdiameter (outer and inner). Oxygen enters the combustion chamber through one of them, and combustion products are discharged into the environment through the other. A very effective solution, especially considering that such a pipe takes up very little space and is installed in one day.

coaxial pipe for boiler

About the benefits of the system

Coaxial gas pipe has a number of significant advantages, thanks to which it has earned such popularity. Firstly, this is the localization of the combustion process, which is carried out by an isolated supply and exhaust of air and, accordingly, combustion products. As a result, there is no mixing of oxygen and gas mixtures. Consequently, the productivity of the equipment increases.

Another plus - in the process of entering the boiler, the air heats up. This is achieved due to the fact that the pipe through which it enters is heated by the waste products of combustion. In general, it is very effective, especially in the cold season. Of course, one cannot ignore the fact that the “pipe in pipe” chimney design itself has smaller dimensions compared to a separate installation. This reduces the number of fasteners, and the complexity of installation is greatly reduced.

A little about the cons of the system

Certainly, there is no perfect system that would not have flaws. In our case, although there are disadvantages, you can simply ignore some of them, since they are insignificant, while others will have to come to terms.

Main disadvantagesuch structures is that their cost is ultimately 20-40% higher than the installation of separate systems. Another problem is the concentric arrangement of pipes with hot and cold air. You have probably noticed icing on such pipes more than once. It is formed due to the accumulation of condensate and its freezing at sub-zero temperatures. You can deal with this by installing an additional drain and insulation. But all this will further increase the price.

Well, the last drawback is the limited length of the coaxial pipe. It's about 4-5 meters. Therefore, if your boiler is not installed near a window or there is no way to remove the coaxial pipe for any reason, this option is not suitable for you.

coaxial gas pipe

About the regulatory framework

You must understand that you can’t just take and install such a chimney, since the installation of a coaxial pipe is carried out taking into account existing requirements and standards. For example, there is a clear rule that says that chimneys can only be installed through the roof. But this does not apply to individual heating, where it is possible to mount horizontal coaxial chimneys. In general, horizontal systems for the removal of combustion products and air supply can only be installed in private houses, and for multi-storey buildings, vertical structures are provided that should rise 1.5 meters above the roof of the building.

coaxial pipe installation

Classification of systems

All modern coaxial chimneysdivided into internal and external. The former are practically not used in residential buildings. Such structures are mounted in special mines or old chimneys. But they must comply with fire safety requirements. In addition, installation of such systems is often very difficult, as well as maintenance.

External coaxial chimneys are deprived of such shortcomings. By the way, they are also classified according to insulation. So, there are insulated and non-insulated. In regions where the air temperature does not fall below -10 degrees Celsius, chimneys can not be additionally insulated. In other cases, there is a risk of partial or complete freezing of pipes. In addition, there are individual and collective chimneys. The first are designed to serve one gas boiler, and the second - for a whole multi-storey building.

Structural composition and material of the chimney

The coaxial system is modular and consists of a large number of typesetting elements. This includes an adapter for a gas boiler, straight pipe sections, connecting elements such as couplings and tees, and much more. True, such components as a coaxial pipe extension, decorative overlays may not be supplied in the kit - you need to buy them yourself if necessary. But the mounting fittings and sealing gaskets, which ensure the strength and tightness of the system, must be present in the kit. When installing such a system, it is desirable to use jumpers. They are necessary to fix the inner pipe relative to the outer one.

Regardingmaterials from which the coaxial pipe is made, most often it is galvanized and stainless steel, which easily withstands high temperatures and does not corrode for a long time. In some cases, it is advisable to use heat-resistant plastic or aluminum. Often, for the consumer, there is no difference what material the pipe will be made of, the main thing is to carry out the correct installation.

vertical coaxial pipe

Chimney selection features

In most cases, the coaxial pipe is supplied with heating equipment, that is, with a gas boiler. That is why almost all manufacturers of heat generators produce chimneys of this type. There is a paragraph in the installation instructions for the equipment that indicates the maximum allowable length of the chimney. This value must not be exceeded under any circumstances. Otherwise, the efficiency of the equipment will be significantly reduced. If the chimney runs on natural draft, that is, the boiler does not have a fan, then a parameter such as the minimum pipe length is entered. If you install a chimney that is shorter in length, then there will be no draft and the combustion products will remain in your apartment or house. The diameter of the pipeline in the passport data is written as 100/140, where the first value is the diameter of the inner pipe, and the second, respectively, is the outer one.

coaxial pipe extension

Do-it-yourself installation of a coaxial pipe

The first thing you should remember is that there are no more than 2folds in your chimney. When installing a horizontal system, install the pipe with an inclination of at least 3 degrees. This is necessary so that the condensate drains on its own. If the coaxial pipe eventually connects to a common chimney, then the angle must be changed in the opposite direction with a slope towards the boiler.

The most important stage of work is drilling a hole in the wall. This must be done with the help of diamond equipment. But it is advisable to carry out such work if the house is being renovated, since there will be quite a lot of noise and dirt. After the hole is ready, it is necessary to lay the pipe, insulate it, and seal it. In general, there is nothing complicated here. The main thing is that the chimney at the bends is well sealed. Also, do not forget about the minimum slope that is necessary for the outflow of condensate.

coaxial pipe length

System installation rules

A vertical coaxial pipe is mounted much easier than a horizontal system. But bringing the chimney to the roof is not always possible. So, if you want the coaxial pipe to be installed correctly, you need to follow a few simple requirements.

So, you can not install the system below ground level. If the distance from the outlet to the ground is less than 1.8 meters, then a deflector grille is installed to protect the pipe from dirt. If there are strong winds in your area, then it is quite possible that the boiler will go out and not work at full capacity. By installing a tin barrier, you can completely and completely solve this problem.problem. Of course, it is advisable to entrust such work to the specialists who installed the heating equipment, but if this is not possible, then by observing these requirements, you can do it on your own.


We talked about what a coaxial pipe is. As you can see, this is a very efficient and practical chimney in terms of performance and space savings. It is quickly mounted and serviced, which, without a doubt, is an important point. If necessary, you can install a coaxial pipe extension, which will slightly increase the total length of the chimney. Pay special attention to insulation, as often such systems completely freeze through. There is nothing good in this. Especially since it happens in the most severe frosts. Although the problem is solved quickly, it is still better that it does not exist. Now you can decide for yourself whether to use such a system or not. Good luck!

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